Like girls, U.S. boys may be hitting puberty earlier

NEW YORK (Reuters Health) - Boys in the United States may be entering puberty earlier than in generations past, a new study has found - suggesting it's not just girls who are developing at younger ages.

Compared to decades-old data, boys seen for well-child visits in 2005 to 2010 were maturing six months to two years sooner, based on their physical development in the genital area.

That's an important finding, both for researchers, who need to figure out why the age of puberty may be creeping down, and for parents, who have to know how and when to discuss changing bodies with their kids, according to the study's lead author.

"They need to talk to their boys earlier than they would have thought about puberty and sexual development and all of those related issues," said Marcia Herman-Giddens, from the University of North Carolina at Chapel Hill.

Even if boys are developing earlier than in the past, that doesn't mean they're also more mature socially and psychologically at younger ages, researchers pointed out.

"Now there's probably a bigger disparity between their physical maturation and their psychosocial maturation," said Dr. Frank Biro, head of adolescent medicine at Cincinnati Children's Medical Center, who wasn't involved in the new analysis.

"People are going to interact with them like they're older," he told Reuters Health.

Data for the new study came from 144 different pediatric offices across the United States and included 4,131 boys age six to 16.

Based on the so-called Tanner stages of development - a technique doctors use to measure how far along in puberty a young person is - genital changes in boys started around the age of nine or 10, and pubic hair appeared between age 10 and 11.5, on average.

Testicle size hit a common cut-off for puberty just before age 10, and full sexual maturity happened at 15 to 16.

In general, African American boys developed earlier than their white and Hispanic peers, Herman-Giddens and her colleagues reported Saturday in Pediatrics.

A study from the 1950s through 1970s of white boys in England - for which the Tanner scale is named - found boys started genital development at age 11.6, on average. Other data through the 1970s also put the start of genital changes between age 11 and 12, and pubic hair development typically between 12 and 13 - about two years later than in the new study.

That's because some of them blame estrogen-like chemicals in the environment for girls' earlier development - and if anything, those same chemicals would be expected to delay sexual maturation in boys.

Herman-Giddens said it's still not clear why boys may also be hitting puberty sooner than in years past. One possible explanation is high rates of obesity (which alters the body's hormone levels).

"I'm concerned that (early puberty) not be considered normal because the reasons it's happening may not be healthy," she told Reuters Health.

Biro agreed more research is needed to figure out what may be driving down the age of puberty.

"It doesn't necessarily have to be a bad thing, but I'm not sure if it's a good thing," he said.

The new study wasn't designed to be a perfectly nationally-representative picture of what's happening across the country. Biro said he thinks puberty is indeed coming earlier in U.S. boys in general - but he added that not everyone agrees.

Regardless of general trends, it's important for parents to pay attention to their own child's development, researchers said, and to know when to start having "the talk."

"Parents need to monitor both their daughters and their sons a little more closely than they would before," Biro said.